In the production of electronic components such as monolithic ceramic capacitors, conventionally, an electronic component body is prepared before external electrodes are formed on outer surfaces thereof. External electrodes of this type are often composed of a sintered electrode layer that is formed by baking a conductive paste and is, for example, plated with Sn.
On the other hand, the mounting of electronic components on, for example, printed circuit boards using a conductive adhesive instead of solder has recently attracted attention as a lead-free mounting method. When an electronic component is mounted on, for example, a printed circuit board with a conductive adhesive, external electrodes are bonded with the conductive adhesive. If the surfaces of the external electrodes are made of, for example, Sn plating, they tend to oxidize during heat treatment for curing the conductive adhesive. Such external electrodes disadvantageously exhibit increased contact resistance and decreased reliability in electrical connection.
Patent Document 1 below discloses an electronic component having external electrodes including laminated sintered electrode layers instead of Sn plating. Specifically, the multilayer ceramic electronic component according to Patent Document 1 includes a ceramic laminate having internal electrodes made of Ni or a Ni alloy and external electrodes formed at both end surfaces of the ceramic laminate. The external electrodes each include a first sintered electrode layer mainly containing Cu or a Cu alloy and a second sintered electrode layer mainly containing Ag or a Ag alloy. According to this publication, the external electrodes are formed by applying a first conductive paste containing Cu or a Cu alloy and a glass frit, applying thereto a second conductive paste containing a metal powder mainly containing Ag or a Ag—Pd alloy and a glass frit, and simultaneously baking the first and second conductive pastes at 700° C.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-158137